Liqour is not allowed and will be confiscated. Some people hide liqour in luggage by rebottling it, say in a mouthwash bottle and mixing thier own mix drinks later. They sometimes check bottles to see what's in them. Usually they will take the items and return it at the end of the cruise.
Some cruiselines do allow wine and champagne though most have a limit on how much you can bring. Some also allow soda, water and juices. Many times I've seen people bring a 24 pack of water on board to save paying $3 bottle.
If you post what line you are taking we can give more info.
11 cruises in 2012, 90 nights at sea visiting 15 countries
8 cruises in 2013, 56 nights at sea visiting 7 countries
Next cruise: None scheduled
PM me if you need a cruisemate for any Europe, transatlantic, or Panama Canal cruises
Date, ship, cost pp